§ 44. Modification of and changes in contracts. a. The board of transportation for and on behalf of the city, from time to time with the consent, in writing, of the bondsmen or sureties of a person, who has contracted with such board or its predecessors to construct, equip, maintain or operate any road, may agree with such contractor upon changes in and modifications of such contract, or of the plans and specifications upon which such road is to be constructed, but no change or modifications in the plans and specifications consented to and authorized pursuant to section twenty-one of this chapter shall be made without the further consent and authorization provided for in such section.

b. The board of transportation, from time to time, but only with the approval of the board of estimate and the mayor, may agree with railroad companies upon changes in and modifications of the terms and conditions of any contract under or pursuant to which any railroad, or any part thereof, has been or is to be constructed, equipped, maintained or operated, and with like approval such contract may be cancelled and replaced by a new contract to include the railroads embraced in such existing contract. The board of transportation may include therein provision for the acquisition by the city of the railroads or any of them or portions of any of them and is authorized and empowered on behalf of the city to accept title thereto or control thereof and to provide for the payment thereof through amortization or otherwise as the board of transportation may determine.

c. Any other provision of this chapter to the contrary notwithstanding, the board of transportation shall not make any new contract or modify any contract for the construction, equipment, maintenance or operation of any railroad without the approval or consent of the board of estimate and the mayor.

d. If any contract for construction or equipment of a railroad or section thereof has been awarded and a part of the work therein required to be performed by the contractor has been done or is in process of being done as to a portion of the route of such road and if another route for a railroad has been or shall be established by the board of transportation under section twenty of this chapter and consented to as provided in section twenty-one of this chapter, which, or a portion of which, in the opinion of such board should in the public interest be substituted in place of a portion of the road to be constructed or equipped under such contract, then the board with the consent of the board of estimate and the mayor, as soon as the detailed plans therefor have been prepared as prescribed in section twenty-two of this chapter, without advertising for proposals, may agree as provided in this subdivision with such contractor upon changes in and modifications of his contract for the purpose of making such substitution. Such agreement in such case may provide, in consideration, among other things, of a surrender by the contractor of his right to construct or equip a designated portion of the road or section or road described in his contract, that such contractor shall complete the construction or equipment of the remainder of the road or section described in such contract and shall in place of the portion surrendered construct or equip a railroad or section of a railroad upon such substituted route and in accordance with the plans and specifications adopted therefor for such sum of money as may be provided in such modifying agreement. As part of the consideration of such modifying agreement, the agreement may also provide that such contractor shall guarantee to the city, with proper and sufficient sureties, that in the event that the city shall enter into such modifying agreement providing for construction of such substituted route or section thereof by the contractor, the cost to the city of providing for the construction of any additional section of such railroad upon such substituted route in continuation of that portion thereof which is to be constructed by the contractor under such modifying agreement, shall not be in excess of an amount specified in such modifying agreement or that if the contract for construction of any such additional section is to be awarded after advertisement for proposals under section seventeen of this chapter, that a responsible bidder for the construction thereof acceptable to the city shall be obtained at a price not exceeding a specified amount.

e. If any contract for equipment, maintenance and operation of a railroad has been made and part of the work of construction thereof has been done or is in process of being done, and if another route for a railroad has been or shall be established by the board of transportation under section twenty of this chapter and consented to as provided in section twenty-one of this chapter, which, or a portion of which, in the opinion of the board in the public interest, should be substituted in place of a portion of the road to be equipped and operated under such contract, for use and operation in connection with or as part of the route, a portion of which has been in part already constructed or is in process of construction, then the board with the consent of the board of estimate and the mayor may agree as provided in this subdivision with the person having the contract for equipment, maintenance and operation of such railroad, upon changes and modifications of such contract. Such agreement in such case may provide, in consideration, among other things, of the surrender by the contractor of his right to equip, maintain and operate a designated portion of the railroad described in his contract, that in place of the portion surrendered, he shall equip, maintain and operate a railroad or portion of a railroad upon such substituted route. The rental to be received by the city under such contract, as changed and modified, representing compensation to the city for the use of such substituted part of such railroad operated thereunder necessarily need not be a portion of the income, earnings or profits from the operation of the railroads combined as provided in subdivision d or subdivision g of section forty of this chapter equal annually, if earned, to the interest and one per centum for sinking fund upon the amount of city bonds issued for the investment of the city in the construction thereof but may be either a specified sum of money or a specified part or proportion of income, earnings or profits of such substituted road, or both a sum of money and a part or proportion of such income, earnings or profits, or may be such portion of the income, earnings and profits of the railroads so combined as may be provided in such modified contract as rental for such substituted railroad and for the other railroads of the city to be equipped, maintained and operated under such contract as so modified.